NEW U7 motor tmotor

Discussion in 'Cinestar 8' started by kjetil tønnesen, Nov 22, 2013.

  1. Bryan Harvey

    Bryan Harvey Member

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    Ahhh, so you think 18" will make those motors work too hard? I would not have guessed that, but I'm not experienced in this area.
    One minute is quite a nice improvement in my opinion, but of course I don't want to stress the motors. I am using 6s by the way.
     
  2. Steve Maller

    Steve Maller UAV Grief Counselor

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    Bryan,
    You may know this already, but there is a definite “sweet spot” for these motors when it comes to their thrust curve. I’m quite amazed at the diligence of Tiger for publishing those awesome tables listing their motors’ characteristics at different throttle levels. If you look, the curves are dramatically different with some prop combinations.

    And one thing to consider when it comes to multirotors is that you almost certainly someday will lose a prop or a ESC, and when that happens, you better not be at 80-90% throttle. If you are, your copter’s not going to be able to stay in the air. The flight controllers (at least my MK did this) will compensate properly for the loss of 1/8 motors, but only if there’s enough overhead to do so. Ask me how I know this (my experience ended well). :eek:
     
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  3. Bryan Harvey

    Bryan Harvey Member

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    Hey Steve,
    Yes I looked at those charts, but to me it just looks like subtle differences between prop sizes. I guess I don't know enough about the scale to note what is significant, what numbers would indicate cause for concern, etc...
     
  4. Chris Fox

    Chris Fox Active Member

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    I'm happy with it ... a lots less fuss than the MK .... after doing the installation, you are left wondering what you have done wrong because it was that simple ..... and it flies well.
     
  5. Zubeyir Mentese

    Zubeyir Mentese New Member

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    Hi guys,
    Great discussion. I want to go with 18 inch props for the extra lifting capacity (I'll be running 6s lipos, x8 config). Any thoughts on the 18 inch Xoars vs the 18 inch Tiger CF props?
    I was thinking of using the Maytech MT75A ESCs. Any thoughts on other options?
    And what about power distribution? Since the U7s are spec’d at 44A/62.7A continuous/max current draw each for a total of 352A/501.6A continuous/max current draw, that exceeds the 400A rating of even the Power Hungry systems boards.
    I'm excited to get my hands on these motors and hear how they sound in the air.
     
  6. Steve Maller

    Steve Maller UAV Grief Counselor

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    I think with that kind of power draw you could lift Lady Gaga.
     
  7. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    352 Amps at 25 volts....let me see....
    Oh....only 8.8 kilowatts.

    WHOA!!!!

    That's just over 6 ETU. (Electric Toaster Units -- dual slice.)

    I can see why you're concerned that those EC5 connectors and/or the solder junctions to the wires might melt, Steve.

    Andy.
     
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  8. Zubeyir Mentese

    Zubeyir Mentese New Member

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    Ha ha, I was thinking of painting the frame white, adding rhinestones, and covering the whole thing in steaks. Drones go avant garde.
    If only we could build copters with just physics equations, you'd only need 10 watts to lift 1kg, 20 watts per kg to make the thing really move.
     
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  9. Zubeyir Mentese

    Zubeyir Mentese New Member

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    This is why I always find it funny when people tell me, "Have you considered putting a solar panel that?" (still not as funny as, "Hey, you know what? You should put a Gopro on that!")
    Maybe it's time we look into power transmission tethers ala Fotokite and Makina Power. How great would it be to be able to use the copter itself to charge your lipos? http://www.makanipower.com/home/
     
  10. Bryan Harvey

    Bryan Harvey Member

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    John Gore, have you noted your ESC temps?

    I am bench testing my U7's in coax configuration with the same Hobbywing 70A ESC's on 6s. I tried the APC 16" MR props and APC 18" MR props. We ran the motors in coax for 5 minutes pulling 25amps total. For some reason the ESC's are getting hot. Ambient air temp is only 40F.
    16" props result in ESC temp of about 125F.
    18" prop showing 140F.

    Motors are running very cool, only maybe 10-20 degrees above ambient.

    Should I be worried about those ESC temps?
     
  11. Borja Casal

    Borja Casal New Member

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    Just a simple question. Has any boddy manage to get a CS8 with full MK electronics (latest) up in the air with the U7 motors? If so, what changes do I need to make on MKtool?
    Thanx

    Borja Casal
    Film director www.paraphernaliafilms.com
    CS8 HL. Mk electronics kw12 Motors
     
  12. Steve Maller

    Steve Maller UAV Grief Counselor

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    Dave King tried, but decided to downgrade to the Tiger U5 after he had problems. I think it could have been the fact that he was using 15” props, as I think the U7 may want larger props. But I’m not sure what the issue was.
     
  13. Dave King

    Dave King Well-Known Member

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    Borja

    Steve is correct. I ran them using stock settings as far as pulse width and timing though. They ran very rough, so rough that my copter just dropped out of the sky. I think that they might work with the MK electronics after some tweaking the settings. I'll let someone else figure it out who might have a spare MK sort it out.
     
  14. Borja Casal

    Borja Casal New Member

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    jesssssssus. Sorry. I hope not much damage was done. So, no idea what cause the problem? I don't know what to do now as I already soldered the wires. It seams that I´m stuck with the U7 as I run out of budget for anymore gear. Esteve, How dramatic was the fall? As I might have to put the U7 and figure it out myself…..only prob is that I do not have a spare MK PDB

    Borja Casal
    Film director www.paraphernaliafilms.com
    CS8 HL. Mk electronics kw12 Motors
     
  15. Dave King

    Dave King Well-Known Member

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    It fell out of the sky about 60 feet high. I sent the info to Holger and he's not even sure what happened. It's possible the vibrations might have messed with the gyros on the board and it just shutdown. The flight recording stopped before it started to descend and nothing really stood out. I would definitely run 17 inch props for this motor. I would also see if you can get some advice on what timing to run as I think the BL settings need serious tweaking. I emailed Tiger but didn't get any response. I was hoping QC would begin testing the motors.

    There is a warning on the MK site about large motors
    Note: The BL-Ctrl 3.0 controller is specifically designed and optimized for our motors. For maximum stability of the MikroKopter setpoints are set almost instantaneously on the motor. If other motors (especially larger power classes) are used with this controller, this fast change of setpoints can easily lead to very high peak currents, which bring the BL-Ctrl control to the limit or an overload. This is no fault of BL-Ctrl3.0 controller, but a systemic property.

    EDIT: One thing I can add is that the only thing that stood out on the data is a big difference between odd and even motor current. However I know for absolutely sure that the motors were aligned and were set correctly. After I ran the U7's for one run and I noticed the behavior I pulled the GPX data, saw the current difference and rechecked the motor alignments and they were all good. Went out for a second pass and it just dropped out of the sky about a minute into the flight.

    One other thing I can add is that I noticed that motor RPM's were much higher just sitting there on the ground than normal.

    Here's the video of the first flight with the U7's and you can hear how fast they are spinning.

     
  16. Borja Casal

    Borja Casal New Member

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    Noboddy else has tried U7? I was reading your conversation over the MK forum. Its strange that nobody else has been experiencing with this best of a motor. I will try different configurations. Any more tips?

    Borja Casal
    Film director www.paraphernaliafilms.com
    CS8 HL. Mk electronics kw12 Motors

     
  17. Dave King

    Dave King Well-Known Member

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    I don't believe anyone has tried it with the MK electronics before. I would turn off active braking for each BL and keep it relatively low to the ground to see how it responds.
     
  18. Borja Casal

    Borja Casal New Member

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    Sorry David. I on that video you posted which electronics are you using?
    Thanx

    Borja Casal
    Film director www.paraphernaliafilms.com
    CS8 HL. Mk electronics kw12 Motors
     
  19. Steve Maller

    Steve Maller UAV Grief Counselor

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    Dave’s using the new MK electronics.
     
  20. Howard Dapp

    Howard Dapp Active Member

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    Bryan, It has been said in quite a few forums that running 'big' ESCs is not necessarily a good thing because if you're not operating anywhere near their max efficiency they tend to heat up and lose efficiency. I believe for most of us here that are building large lifters, 40a is more than enough. Forget ecalc and the motor @ maximum column, you will never need to go max throttle on a multi if you're running the proper setup.
     
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